Which two are prerequisites for creating a standby data…

Which two are prerequisites for creating a standby database using Enterprise Manager cloud control?

A.
The primary database must have FORCE LOGGING enabled.

B.
The primary database must be in archivelog mode.

C.
A backup of the primary database must exist.

D.
The primary host and the proposed standby database host must run the same operating system.

E.
The primary database instance must be started using an SPFILE.

F.
The primary database must have flashback enabled.

Explanation:
A: Before you create a standby database you must first ensure the primary database is properly configured.
Place the primary database in FORCE LOGGING mode.
B: If archiving is not enabled, issue the following SQL statements to put the primary database in ARCHIVELOG
mode and enable automatic archiving:
SQL> SHUTDOWN IMMEDIATE;
SQL> STARTUP MOUNT;
SQL> ALTER DATABASE ARCHIVELOG;
SQL> ALTER DATABASE OPEN;
https://docs.oracle.com/database/121/SBYDB/create_ps.htm#SBYDB4719